The invention relates to an aromatization process for converting a cracked gasoline feedstock to yield incremental aromatics with a low rate of coke formation during the conversion of such cracked gasoline feedstock using a modified zeolite material.
It is known to catalytically crack heavy hydrocarbons, particularly hydrocarbons in the gas oil boiling range, to lower boiling hydrocarbons such as those that are in the gasoline boiling range. Specifically, the reaction products of the catalytic cracking processes contain a multitude of hydrocarbons such as unconverted C.sub.5 + alkanes, lower alkanes (methane, ethane, propane), lower alkenes (ethylene and propylene), C.sub.6 -C.sub.8 aromatic hydrocarbons (benzene, toluene, xylenes, and ethylbenzene), and C.sub.9 + aromatic hydrocarbons. It can be desirable to further process the cracked gasoline product from a catalytic cracking process in order to increase the yield of more valuable aromatic compounds. This may be done with the use of certain zeolite catalyst materials.
One concern with the use of zeolite catalysts in the conversion of hydrocarbons to aromatic hydrocarbons, or lower olefins, or both, is the excessive production of coke during the conversion reaction. Coke formed during the zeolite catalyzed aromatization of hydrocarbons tends to cause catalyst deactivation. It is desirable to improve processes for the aromatization of hydrocarbons and the formation of lower olefins from hydrocarbons by minimizing the amount of coke formed during such processes. It is also desirable to have a zeolite catalyst that is useful in producing significant quantities of the aromatic and olefin conversion products.